Re: [PATCH v2 2/8] block,fs,mm: IO cgroup tracking for buffered write
From: Justin TerAvest
Date: Wed Mar 23 2011 - 13:21:31 EST
On Tue, Mar 22, 2011 at 9:52 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@xxxxxxxxxxxxxx> wrote:
> On Tue, 22 Mar 2011 16:08:49 -0700
> Justin TerAvest <teravest@xxxxxxxxxx> wrote:
>
>> +static inline void page_cgroup_set_blkio_id(struct page_cgroup *pc,
>> + unsigned long id)
>> +{
>> + unsigned long old, new, prev;
>> +
>> + /* pc->flags isn't lock protected, so we must cmpxchg. */
>> + WARN_ON(id >= (1UL << PAGE_TRACKING_ID_BITS));
>> + do {
>> + new = old = pc->flags;
>> + new &= (1UL << PAGE_TRACKING_ID_SHIFT) - 1;
>> + new |= (unsigned long)(id << PAGE_TRACKING_ID_SHIFT);
>> + prev = cmpxchg(&pc->flags, old, new);
>> + } while (prev != old);
>
> How to support archs which doesn't have cmpxchg ?
> At least, you need take care of compile error.
Hi Kame,
Is there really no generic cmpxchg()? I thought that was what
include/asm-generic/cmpxchg-local.h was for.
Thanks,
Justin
>
> Thanks,
> -Kame
>
>
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